One form of pneumatic device, referred to as either an air mover or air pump, has an elongate tubular body defining a through bore. Between the ends of the bore, the body, or a fitting secured thereto, defines an annular chamber that extends substantially concentrically around the bore. Pressurised air is able to be supplied to the chamber for discharge via a plurality of passages, thus providing communication between the chamber and the bore; the passages opening towards one end of the bore such that the discharged air issues from that end. The pressurised air generates a reduction in pressure upstream of the bore from the passages, such that air can be drawn along the bore.
The device functions either as an air mover or an air pump and can be used, for example, for; vacuum generation; to transport particulate material; or to purge gases from, or to supply gas to, an enclosure or work area. Typically, the passages providing communication between the chamber and bore extend substantially parallel to the axis of the bore, or they are inclined toward the bore so as to converge at an axial location downstream of the chamber.
An improved form of pneumatic device of that type is disclosed in my Australian patent 607079. A pump device having some similarity to such pneumatic devices, and suitable for pumping a range of materials, is disclosed in my Australian patent 627043. Also, a somewhat related apparatus for making snow is disclosed in my Australian patent specification 625655. The present invention is concerned with a further development in the context of these devices, and is suitable for use as a pump and/or mixing device.